How should I build a realistic purchase budget?

Run a household stress test

Begin with money you can use without borrowing, selling something unexpectedly, or counting on a payment that has not arrived. Subtract transaction cash and the move. Then decide what reserve must remain for your household and the property. Use scenarios rather than a universal percentage: a condo buyer may face an assessment and an insurance deductible; a two-flat buyer may face vacancy and a shared heating repair; a house buyer may need exterior work soon after moving.

On the monthly side, write every ownership cost beside the mortgage payment, including items paid directly and irregular bills divided into a monthly planning amount. Compare that total with take-home income and your other commitments. Finally, change two inputs together, such as higher insurance and an early repair. If the revised plan depends on a future raise, immediate refinance, or uninterrupted rental income, document that dependency and decide whether you can carry it. This is a planning exercise, not a prediction of actual expenses or a lender's approval standard.

• Show transaction cash separately.
• Test two adverse changes together.
• Set a reserve floor before choosing the down payment.

Related resources